Unit: Energy and Control

 One hundred million volts! That’s how much electricity is in one bolt of lightening. Every day the Earth is struck by lightening more than times! And the temperature of each bolt of lightening is about Celsius.

 Blow up one of the balloons. Tie it closed. Rub it against a piece of felt. This give it a charge.  Hold the balloon just above the hair on your arm or the top of your head. What happens? Now try to make the balloon stick to a wall.  Inflate a second balloon. Tie one balloon to each end of a piece of string 1m long. Rub both balloons with the felt to give them static charge. Hold the middle of the string and let the balloons hang down. Then hold the cardboard between the balloons and observe what happens.

 Find other objects that can be charges the static electricity. Design a method to test them.  Rub your feet as you walk across a carpet. Then touch a metal object like a door knob. What happens?  Make a “kissing” balloon. Hang a balloon on a string from a door frame or from a ceiling. Make sure it hangs at the same height as your face. Draw a face on the balloon. Rub the nose of the balloon face with the felt cloth. Move your face close to the balloon. What happens?

 What did you do to charge the balloon with static electricity?  What happened to the hair on your arm or head?  Why does the ballo0n stick to the wall?  What made the two charges balloons push away from each other?  What does the cardboard cause the balloons to swing together?

 How do you know if something has been charged by static electricity?  Can you think of times when you encounter static electricity?  Write a paragraph in your notebook to describe static electricity.

 As a class find a way to light the bulb  Trace the path of the electricity with your finger. Start from the negative terminal of the batter. The electricity goes in a complete loop from the battery, through the filament of the bulb, and back into the battery.  How many ways can you light the bulb using only the material?

 Draw a diagram of your circuit. Label each part correctly. Use arrows in your diagram to show the complete path of electricity.  In this circuit, the electrical energy is converted into what other forms of energy?  What do static electricity and current electricity have in common? How are they different?  What is a short circuit? Why are short circuit dangerous?

 Electricity makes things happen. For example, energy makes you move, energy makes light shine, and energy makes the Earth warm. There are many forms of energy. Electricity is one kind. What do you imagine when you think of electricity? Do you think of lights, televisions, radios, and computers? We have these devices only because people have found ways to control and use electrical energy.

 Electrical Energy is the energy of electrons. Electrons are part of every atom and some of the smallest particles in the universe. Electrons have a negative charge. Because some atoms lost electrons easily and others gain them easily, electrons can move from one material to another. Electrons carry electrical charge.

 If a material gains or loses electrons, it develops charge called “static electricity.” “Static” means that the electric charge does not move. When fur is rubbed against plastic, electrons move from the fur to the plastic, forming a static charge on both materials. The fur develops a positive charge because fur gives up electrons easily. The plastic develops a negative charge because plastic gains electrons easily.

 When two materials have the same charge they repel (push away) each other. For example, two balloons repel each other because each has a negative charge. If your hair gains a large positive charge, it actually stands up on end because each strang of hair repels its neighbours.

 When you rub your feet across a carpet, a negative charge moves into your body. Then, if you touch a metal object such as a doorknob, you get a small shock because the electrons rush out of your body and into the metal object. If the negative charge in your body is large enough, you see a small spark leap from your finger just before you touch the metal object.

 The small spark is like lightning. A lightning bolt is a huge spark full of electrons that flow between a charged cloud and either another charged cloud or the ground. The electrostatic charge in a cloud is so great that the cloud does not have to touch the ground for the electrons to flow. They leap through the air as lightning!

 When electricity moves it is called current electricity. The spark from your finer to the doorknob, a lightning bolt, and the electricity in a wire are all current electricity. Electric current always flows from negative to positive.  An electric circuit is electricity that flows in a loop. It begins at a source of electrons and travels through a device and back to the electron source.

 An electric circuit has 3 parts: a power source (a battery), a material to conduct the energy (the copper wire), and something to resist or use the energy (a light bulb). If electricity flows directly from negative to positive without being slowed down by a resister device, you have a short circuit. A short circuit can drain the battery quickly because there is little resistance. As a result of the fast-moving electrons, the wire heats up quickly. The wire from even a little battery can burn your fingers.